SAN SALVADOR (Reuters) - Police and soldiers in El Salvador may have committed extrajudicial killings and used excessive force in their battle against violent street gangs in the Central American country, the United Nations said on Monday.

Agnes Callamard, the UN Special Rapporteur on extrajudicial, summary or arbitrary executions, said her findings did not indicate a state policy that came from above but rather the actions of a few members of the security forces. Callamard was on a two-week tour of El Salvador.

"I have found a pattern of behavior between security personnel that could be considered as extrajudicial killings," Callamard told a news conference, without giving further details.

"This is fomented more by weak answers from public institutions," she said.

The United Nations asked the Salvadoran government to investigate cases of extrajudicial killings by authorities and try those responsible.

Human rights organizations have denounced extrajudicial killings and abuse of force by operatives from the government of President Salvador Sanchez Ceren.

"We understand as an institution that there could be some police officers that don't do their job well, but the institutional line is that all working police should do things according to the law," police spokeswoman Evelyn Marroquin said.

El Salvador had a homicide rate of 60 per 100,000 people in 2017, one of the highest in the world.